If you know someone who eats whatever they want and never seems to gain any weight, it’s normal to feel a little envious. However, they could be doing their body just as much harm as they would by gaining weight. This is according to a new study that reveals the quality of your food counts more than your weight when it comes to cancer risk.

Scientists already knew that obesity raises the risk of certain types of cancer, namely that of the kidney, breast, pancreas, esophagus, colon and uterus. But these researchers set out to find out how dietary energy density (DED) – the ratio of energy to food weight – affects your cancer risk.

DED is considered one of the best measurements of food quality as it looks at the relationship of the calories in a food to its nutrients. Foods with more calories for each gram of weight have higher DEDs. This means that whole foods that pack a lot of nutrients into very few calories like lean protein, vegetables, beans and fruits are low in DEDs.

Processed foods, on the other hand, are high in DEDs because you must eat more of them to get the nutrients you need. Foods like pizzas and hamburgers fall under this category. Not surprisingly, past studies have linked the regular consumption of these foods with weight gain in adults.

Researchers looked at data from 90,000 post-menopausal women who took part in the Women’s Health Initiative. They examined their diets and any cancer diagnoses, and they discovered that the women who ate higher-DED foods had a 10 percent greater likelihood of developing an obesity-related cancer regardless of their body mass index. Not only that, they found that the higher risk was limited to women who had a normal weight at the program’s inception.

University of Arizona Professor of Health Promotion Sciences Dr. Cynthia A. Thomson, the study’s lead investigator, expressed her surprise at the finding, saying: “The demonstrated effect in normal-weight women in relation to risk for obesity-related cancers is novel and contrary to our hypothesis. This finding suggests that weight management alone may not protect against obesity-related cancers should women favor a diet pattern indicative of high energy density.”

Even though restricting the amount of energy-dense foods you consume can help keep your weight down, it appears that gaining weight was not the sole reason women who started out at normal weights saw their cancer risk grow. The researchers believe that the higher-DED diet of those normal weight women led to a metabolic dysregulation independent of their weight, and this is known to raise a person’s risk of cancer. Their findings were published in the Journal of the Academy of Nutrition and Dietetics.

It’s never too late to change your diet for the better

Next, scientists would like to investigate if DED plays a similar role in the risk of cancer among other groups of people, such as men and young women. In the meantime, however, this is very useful information that post-menopausal women can use to guide their eating choices. Women in this group should opt for low-DED foods, even if they have a healthy weight.

Best of all, as Dr. Thomson pointed out, this is a cancer risk factor that women can control. Changing their diet to choose low-DED foods can make a big difference, so there really is no reason not to make some dietary changes. Anyone can benefit from opting for healthy, unprocessed foods that provide a broad range of nutrients, and it’s never too late to start eating this way.

The bottom line is that even though you might be able to eat whatever you want and stay the same size, you really shouldn’t – unless you want to raise your cancer risk.